Electric discharge lamp and starting device



April 4, 1944.

H. J. M

OCARTHY 2,346,109

ELECTRIC DISCHARGE LAMP AND STARTING DEVICE Filed Nov. 8, 1941 P Fig. 2A

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INSULATION INSULATION IN VENT OR ATTORNEY April 4, 1944. H MCCA THY 2,346,109

ELECTRIC DISCHARGE LAMP AND STARTING DEVICE I? Filed Nov. 8, 1941 2 Sheets- Sheet 2 INSULA T/ON He my J. Mc Carthy, MENTOR.

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ATTORNEY been Patented Apr. 4, 1944 ELECTRIC DISCHARGE LAMP AND STARTING DEVICE Henry J, McCarthy, Danvers,

Sylvania Electric Products of Massachusetts Mass., assignor to Inc., a corporation Application November 8, 1941, Serial No. 418,358

4 Claims.

This invention relatesto thermal relays and more'particularly to thermal relays of the type adaptable for use in connection with auxiliary starting apparatus for and more particularly fluorescent lamps.

An object of this inventiori is to provide a thermal 'relay capable of delicate adjustment and Positive action.

Another object is to provide athermal relay of a basic type capable of several modifications thereby insuring a design for each specialized purpose.

, A further object is to provide a thermal relay which will enable the pre-heating of the electrodes oi the discharge device in a minimum period of time.

Other objects, advantages and features will be apparent from the following specification taken in conjunction with the accompanying drawings in which: i

Figures l7 inclusive consist of-aseries of circuit diagrams, noted with the letter a and a corresponding series of schematic diagrams, noted with the letters b and c, 01' one or more thermal relays in which each circuit may be employed.

Figure 8 is a side elevational view of a thermal relay embodying this invention;

Figure 9 is a projection of the thermal relay of Figure 8.

Figure 10 is a schematic diagram of a lamp and a circuit with which any one of the several relays of Figures 1-7 may be used.

found necessary to heat the filamentary electrodes thereof for a brief interval in order that they may support the discharge across the lamp. For lamps of the same size and ,wattage, the length of this heating interval is substantially uniform in duration. However, it may well happen that. a certain lamp of the same size and wattage, mayrequire a longer pre-heating interval for the filamentary electrodes thereof than another. With this in mind, I have devised a thermal relay which is so constructed that it will not only initiate aprimary pre-heating period but will also provide any number of secondary pre-heating periods necessary in order to start the lamp.

My invention consists fundamentally of a bimetallic strip, a high resistance rod associated therewith in a manner to conduct heat to the bimetallic strip yet insulated therefrom, and a pair of electrical contacts associated with an end of said bimetallic strip, one of said contacts being the operation. of a fluorescent lamp, it has electric discharge devices normally closed with an end of the strip and the other being normally open with respect thereto.

The first pre-heating interval is initiated through the contact normally closed with the bimetallic strip.-. In this way no time is lost by having to wait for the relay elements to assume certain positions before the filamentary electrodes start to heat. In this way they start to heat as soon as the lamp starting apparatus is connected to the line. The length of time it takes to heat the bimetal sufiiciently to cause it to break from its normally closed association with one of the contacts is calculated to be substantially the same as that normally necessaryto heat the filamentary electrodes sufliciently to support the discharge across the lamp. This heating of the bi metal during the initial pre-heating period is accomplished through the contact with which it is normally closed. This contact is one of high contact resistance and may consist of a heating coil or resistance in heat-imparting relation thereto or it may take the form of a carbon contact.

if for any reason the lamp arc fails to strike after this initial preheating period, the line voltage, which'is across the resistance rod once the bimetal breaks from the contact with which it is normally closed, will heat the bimetal sufilciently to draw it over and close with the second electrical contact thereby initiating the second electrode pre-heating period. This second period lasts as long as it takes for the bimetal to cool sufficiently to break from its position closed with the second electrical contact, the strip starting to cool as soon as it closed with the contact in as much as the resistance rod which was imparting the heat thereto is short-circuited by the closing.

of the bimetal with the contac When this second electrode pre-heating interval has been terminated by the breaking of the bimetal from thesecond contact, the lamp arc may or may not strike. If it doesn't, line voltage will again be across the resistance rod and another electrode pre-heating period will be initiated as soon as the heat from the resistance rod causes the bimetai to close with the second electrical contact. This cycle of operation will continue until the lamp arc finally strikes.

When the lamp does light, the voltage across the resistance rod will be about one-half line voltage, 1. e., about the same as the voltage across the lamp. in terms of heat-imparting ability, it means that the resistance rod conducts enough .heat to the bimetallic strip to prevent it from iirst mentioned electrical contact, yet it does not conduct enough heat to the bimetal to cause it to move over and close with the second mentioned electrical contact. Thus under lamp operating conditions, the free end of the bimetallic strip assumes a position midway between the two elec- 'trical contacts.

In the several figures of the accompanying drawings I have shown modifications of the above- ,described principles both with respect to circuits therefor and the relays in which they may be used. It should be noted that in that section of the everal figures noted with a b or a c, the electrical contacts are denoted by arrow heads. It should rial. The heater member i is not shown but could be mounted and connected as shown in Figure B. In the actual showing of Figure 8, the contact 3 performs a similar-heating function to that of heater I in the other figures. The carbon contact 3, normally? closed with the bimetallic armature 4 i supported on the arm l8 fromthe strip IS on which the re-starting contact I is mounted. This strip is serves as.a compensator toprovide for'ambient temperature changes and insures the proper relative displacement of the several relay elements. The bimetallic strip 4 is supported from thelead-in wire 9 or electrically connected thereto by the arm i2 and is bent around the resistance rod 2 which may be of about 30,000 ohm resistance, and which is therefrom to be distorted sumcientiy to cause it to move over and close with the contact 1.

Once this closing of the strip s with the contact I has been established, a second pre-heating of the electrodes of the discharge device will take place. The circuit will then be through the bimetallic strip 8 and the contact I. Thus the resistance rod. will no longer impart heat to the bimetallic strip and the strip'will consequently cool, breaking from contact I at approximately the same time that the electrodes of the discharge d'evice are calculated to have been heated sufiiciently to support the discharge thereacross.

If the arc strikes, lamp operating voltage will be across the resistance rod 2. Since this is about half line voltage, the heat from the rod 2 will heat the bimetallic strip enough to prevent it from returning to its initial position closed with the contact 3 but not enough to cause itto move overand close with the contact I. If the are again fails to strike, the line voltage will be is supported from the lead-in wire 9 by the arm coated with a material capable of rendering it insulated from the bimetallic strip yet capable of conducting heat thereto. The elements SI and 32 are electrical contacts on the free end of the bimetallic strip 4.

Figure 9 shows more clearly how the several and the relative positions they assume. As pointed out in the description of Figure 8, the bimetallic armature is electrically connected to w the lead-in wire 0 through the support l2. These lic strip 4. When the line voltage is placed across the circuit terminals 5v and 8, the electrodes oi the electric discharge device to which the relay is connected will start to heat. The heating coil l is calculated to heat the bimetallic strip 4 enough to cause it to break from its normally closed position. with the electrical contact 3 at approigim'ately the same time that the electrodes of the discharge device have become heated sufficiently to support the discharge thereacross. If the arc fails to strike, the full line voltage now being across the resistance rod 2, the bimetallic strip 4 will-be sufliciently heated by the heat elements of the relayof Figure 8 are mounted across the resistance rod 2 and the strip 4 will again move over and close with contact 1.

Figure 1b shows the elements of the relay of Figure 1a mounted on the base 8 with the lead-in wires 9 and I0 electrically connecting the relay to the base pins II. The bimetallic armature 4 l2 and is bent around the resistance rod 2. The

contacts 3 and l are supported on the arm l3' and respectively, the contact 3 being disposed on one side ofthe strip 4 and the contact 1 on the other side.

In Figure 2a, the heating coil i is connected in parallel with the resistance rod 2 and in series with the bimetallic strip 4. The heat from the heating coil i will cause the bimetallic strip 4 to break from its position normally closed with the contact I to terminate the first electrode preheating period. If the lamp fails to light, the full line voltage will be across the resistance rod 2 which will then heat the bimetallic strip 4 enough to cause it to close with the contact 1 to provide a second electrode pre-heating period. This second period is terminated when the cooling strip 4 breaks from its position closed with the contact I. The heat from the heating coil I, during operation of the lamp is enough to keep the bimetal 4 from returning to its original position closed with the contact 3 whereas the heat from the resistance rod 2 is not enough to close the bimetal 4 with the contact .1 under lamp operating conditions.

Figure 2b, shows the'elements of th relay of Figure 2a, mounted on the base 8 with the lead-in wires 9 and Ill electrically connecting the relay to the base pins l I. I 1

In Figure 3a, the heating coilis mounted on the bimetallic armature 4 and has the insulatin member 15 disposed therebetween at a point ad-' the. initial pre-heating period the bimetal 4. the

heating coil I and the insulating member l5 will 1 all move as a unit breaking away from the normally closed position with contact 3. If the lamp arc fails to strike, the line voltage now across the resistance rod 2 will heatthe strip 4 enough to cause it to move over and close with the contact I and thereby initiate a second electrode preheating Period. Figure 3b illustrates schematically the manner in which these elements may be assembled. 1

In the relay of Figure 4a, the heating coil l is connected in series with a second bimetallicstrip l6. This insures more positive breaking of the bimetallic strip or it may be wound 4 from its normally closed position with the contact 3 for the heat from the heating coil I will tend to distort the strip IS in one direction and such heat as passes to the strip 4 through the contact 3 on the strip I6 will tend to distort the strip 4 in the opposite direction. When the strip 4 breaks away from the contact 3 the initial pre-heating period is terminated thereby. If the lamp arc fails to strike, the full line voltage now across the resistance rod 2 will heat the strip 4 enough to cause it to close with the contact 1 and initiate a second pre-heating period. Figure 4b is a schematic diagram of the relay using the circuit of Figure 4a.

In Figure a, the heating coil I through the contact 3 will heat the bimetallic. strip 4, normally closed with the contact 3, sufilciently to cause the bimetal 4 to break from the contact 3 and terminate the initial electrode preheating period. The second pre-heating period is imparted if the lamp arc fails to strike the first time when the bimetal 4 is drawn over to close with the contact 1 by the heat imparted thereto by reason or the full line voltage being across the resistance rod 2. The relay of Figure 5 is similar to that shown in my copending application, Serial Number 335,968, filed May 18, 1940.

The elements of a circuit of this type may be of this figure, Figure 5. The heating coil I may be wound around the resistance rod 2 as shown in b or it may take the form of a contact of high contact resistance such as carbon as shown in c.

In Figure 60, two bimetallic strips, 4 and I 6 are employed, strip '4 being connected in series with the heating coil I and normally closed with the contact 3 operating to control the first electrode pre-heating period while bimetai I6, heated by the full line voltage across the resistance rod 2 in case the lamp arc fails to strike after the first heating period moves over and closes with contact 1 to initiate the secondary pro-heating period. I The heating coil may join the two b metallic strips '4 and I 8 as shown in Figure 6 around the resistance rod 2 as shown in Figure 6c.

The operation of the circuit as shown in Figure 7a, depends on the differential heat between the heating coil I and the resistance rod 2. The heat from the coil is enough to cause the bimetallic strip .4 to break from the contact 3 to terminate the initial electrode pre-heating period but it is not enough to cause it to stay closed with the contact I after the secondary electrode pre- 1 heating period has elapsed. Figure 7b shows how the elements oi the relay may be assembled in accordance with the circuit oi Figure 7a.

In Figure 10, the lam 2D with the filamentary electrodes II and 22 sealed may have a filling of an inert gas such as argon and a vapor such as mercury sealed therein. The lead-in wire 23 from one end of filament II may be connected to one end of th power line at each end thereof ance coil 24 through the lead-in wire it to the I gether by the lines 28 and 21 through the relay 2 8 which may be of a construction similar to any of those shown and described above. A condenser 29 may be placed across the resistance rod 2 to cut down radio interference due to the operation of the lamp and switch. A condenser of .006 microi'arad has proven to be advantageous.

What I claim is:

1. A thermal relay comprising: a bimetallic strip; a resistance rod in heat-conducting relationship with said bimetallic strip, yet insulated therefrom; a heating coil wound around said re sistance rod, said coil being connected in series with said strip and in parallel with said resistance rod; an electrical contact connected to an end of said resistance rod through a path having a low resistance compared with the resistance of the resistance rod and normally open with respect to said bimetallic strip when the circuit therethrough is unenergized;-and a second electrical contact connected to an end of said resistance rod and normally closed with said bimetallic strip when the circuit therethrough is unenergized.

2. A thermal relay comprising: a bimetallic strip; a resistance rod in heat-conducting relationship with said bimetallic strip, yet insulated therefrom; a heating coil wound around said resistance rod, said coil being electrically connected in series with said resistance rod; an electrical contact in series with said heating coil, saidcontact being normally closed with said bimetallic strip when the circuit therethrough is unenergized; and a second electrical contact connected to an end of said resistance rod through a path having a low resistance compared with the resistance of the resistance rod and normally open with respect to said bimetallic strip when the circuit therethrough is unenergized.-

3. A thermal relay circuit comprising a heater member and two possible paths of short circuit therefor; contacts, in each of said paths, separable to break their respective paths and so arranged that when the relay circuit is unenergized-and at rest, one of said paths is closed and the other broken; another heater member in said hook-like thermally responsive bimetallic member fixed at its short end to the panel-like upright, and having its long end free to move; a high resistance rod supported from said panellike upright and passing through the looped portion of the hook to be in heating range 01' said thermally responsive member; a contact closed to the free end of said thermally responsive member when said resistor is unenergized; and a low-resistance unit placed in heating range or said thermally responsive member to cause said member to move away from said contact when said unit is ergized. HENRY J. MCCARTHY. 

